The most maligned figure in the game since Shane Watson’s departure, the veteran batsman is set to play a critical role at No.3 when Australia start the series against a tough and imposing India at Adelaide Oval on Thursday.

And he will do it with a smile on his face.

As selectors consider an opening combination of Aaron Finch and Usman Khawaja, with Peter Handscomb favoured to edge out Victorian teammate Marcus Harris, Marsh’s vast experience and superb form are critical. And the 35-year-old left-hander is about to be given the chance to avenge his record poor return against India in 2011-12 when he produced just 17 runs in four matches in the worst series by any No.3 in Test history.

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Marsh is a far different batsman and person now. He is in the best form of his life, even with the third-ball duck against NSW at Optus Stadium on Thursday that was just his third single-figure dismissal for WA in the past three years.

It followed his superb 81 in the first innings as he defied NSW’s strong attack for nearly five hours in bowler-friendly conditions.

Marsh batted at No.3 in both innings, the same position where he produced 163 not out in a successful run chase against SA at Adelaide Oval last month.

“I’m not sure if I have ever batted better but I know I just have to keep it simple and keep having fun,” Marsh said.

“I’m really relaxed, I’m not putting any pressure on myself and I’m just preparing well and playing with a smile on my face. I haven’t tried to worry about stuff and I’ve just gone out and given it a crack.

Camera IconMarsh was tremendous last summer.Picture: Getty Images

“That’s all I’ve done for the past three or four weeks.

“I haven’t worried about what’s been written about me, about whether I get picked or not and I’ve just gone out and enjoyed batting.”

Marsh has played 34 Tests in nine separate stints, being dropped three times, injured twice and making way for a returning senior batsman on the other three occasions. But he has never held such a senior role in the team as he does this summer.

Marsh said his three coaches — Australian coach Justin Langer, WA mentor Adam Voges and his batting adviser Scott Meuleman — had played key roles in his recent development which has seen him mirror Voges by playing his best cricket in his mid-30s.

“Having a positive mindset has really helped me,” Marsh said.

He has responded by being WA’s best batsman by a significant margin, a condition that he could replicate at Test level this summer.